Melting ice has changed the shape of Earth, making it more bulgy at the equator. Scientists understand most of the things that affect the planet’s shape, such as tides and weather, but satellite measurements between 1975 and 2009 show an unexplained change starting in the mid-1990s. Researchers at the University of Colorado at Boulder have now combined those measurements with data from the gravity-sensing GRACE satellites, and report that ice melting off Greenland and Antarctica is to blame. Solid ice near the poles has transformed into liquid water distributed around the planet, the team reports in an upcoming Geophysical Research Letters. —Alexandra Witze
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